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Oozie job failed with "Could not find or load main class org.apache.hadoop.mapreduce.v2.app.MRAppMaster"

Problem: Oozie launcher mapper failed with the below error:

Could not find or load main class org.apache.hadoop.mapreduce.v2.app.MRAppMaster

Solution:

The above error indicates that yarn classpath does not include the jars containing the required MRAppMaster class on the Oozie server / client. 

You will need to setup Yarn application client libraries with updated yarn-site.xml containing correct yarn.application.classpath. Once you have ensured that yarn client & yarn-site.xml is setup correctly, restart Oozie server so that it can pick up the changes. This is not problem with Oozie, but oozie fails due to incorrect configuration.

Example:

<property>
<name>yarn.application.classpath</name>
<value>$HADOOP_CONF_DIR,$HADOOP_COMMON_HOME/*,$HADOOP_COMMON_HOME/lib/*,$HADOOP_HDFS_HOME/*,$HADOOP_HDFS_HOME/lib/*,$HADOOP_MAPRED_HOME/*,$HADOOP_MAPRED_HOME/lib/*,$HADOOP_YARN_HOME/*,$HADOOP_YARN_HOME/lib/*,$USS_HOME/*,$USS_CONF</value>
</property>

where all the above variables are setup correctly using the corresponding <daemon>-config.sh scripts. Ex: hdfs-config.sh

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